Need to drill out some spindles.....

[nova65ss]

I am trying to enlarge the steering arm and spindle bolt holes on my Nova to 1/2" for a larger bolt. Tried with a new drill bit and my air powered drill but made it about a 1/4" and found out how tough that steel is. Any ideas on what I can do short of taking it to a machine shop? Thanks,

 

[KenS]

You're drill speed with the air-powered drill is way too fast.

Do yourself a favor and watch this video. It is a little slow-paced, but I promise it will be time well spent. It will help you understand the correlation between drill size and speed:

http://techtv.mit.edu/videos/130-span-classhighlightmachinespan-shop-2

Another hint: Try to use a little cutting fluid and be sure not to overheat your drill bit. Slow and patient is the way to get through this hole.

 

[nova65ss]

Yeah I don't have a drill press so it looks like I will just take it somewhere and let them do it. Thanks,

 

[KenS]

You don't need a drill press. Just a slower drill speed. Trying to burn your way through a hole with smoking drill bit running at 10,000 RPM is a recipe for failure. A little patience and you will be through in a few minutes.

Of course there's nothing wrong with letting someone do it for you-- other than the sense of satisfaction that comes with doing it right yourself and a few more bucks that stay in your pocket.

 

[nova65ss]

I will try it slower and see what happens. Thanks for the tips!

 

[Vicegrip]

Use coolant too. Light oil or water. some metals are hardened through or deeply case hardened and will just eat drills.

 

[MXtras]

The basic rule for any drilling is that if you are making noise you aren't making chips - you are ruining the cutting edges of the drill.

You will have better results by using an electric, variable speed drill.

Scott

 

[Herb]

Yep, ditch that air drill or slow the speed WAY down, use some lube (no synthetics here) and pressure.

 

[bomber]

and a sharp (make that SHARP, as in new) bit . . . . won't wander as much

 

[OldCarGuy]

If a high speed drill bit fails. Use a carbide inserted spade drill bit. More commonly known as a masonry drill bit. They do wonders in tough forgings.

 

[MXtras]

There are a lot of different things you can do to the end of the drill in this situation.

To do what you describe by hand, a sharp corner is going to grab and possibly break the drill. I suggest using a drill with a neutral rake, minimal clearance and even a chamfer or radius on the corner. This doesn't mean its dull, it means it has different, less aggressive cutting geometry and the cutting edge will be stronger and live longer. Grinding small flats on the leading edge of each flute will create a stronger edge that is far more controllable than a sharp edge - less grabbing and longer life.

If you use OldCarGuy's suggestion, keep in mind the masonary drills create a lot of heat when used for said purpose. It's a good suggestion, though - the carbide is a lot stronger than a typical drill. Masonary drills don't have cutting geometry, though - they basically push material out of the way when used on steel. I assume you have no way to grind carbide otherwise there are a few things you can do to a standard masonary bit to make them cut fairly well.

It's possible that you have work hardened this area of your part so you might be in for a bit of work now. Keep the generated heat to a minimum.

If you are not making chips, you're just making heat.

Scott

 

[pirana]

I would add that you might try stepping up your hole size a little at a time. That usually works for me when drilling hard material or something that breaks easily. I'm also a fan of Tap Magic for drilling holes.